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Tang Q, Lan T, Zhou C, Gao J, Wu L, Wei H, Li W, Tang Z, Tang W, Diao H, Xu Y, Peng X, Pang J, Zhao X, Sun Z. Nutrition strategies to control post-weaning diarrhea of piglets: From the perspective of feeds. ANIMAL NUTRITION (ZHONGGUO XU MU SHOU YI XUE HUI) 2024; 17:297-311. [PMID: 38800731 PMCID: PMC11127239 DOI: 10.1016/j.aninu.2024.03.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Revised: 01/26/2024] [Accepted: 03/21/2024] [Indexed: 05/29/2024]
Abstract
Post-weaning diarrhea (PWD) is a globally significant threat to the swine industry. Historically, antibiotics as well as high doses of zinc oxide and copper sulfate have been commonly used to control PWD. However, the development of bacterial resistance and environmental pollution have created an interest in alternative strategies. In recent years, the research surrounding these alternative strategies and the mechanisms of piglet diarrhea has been continually updated. Mechanically, diarrhea in piglets is a result of an imbalance in intestinal fluid and electrolyte absorption and secretion. In general, enterotoxigenic Escherichia coli (ETEC) and diarrheal viruses are known to cause an imbalance in the absorption and secretion of intestinal fluids and electrolytes in piglets, resulting in diarrhea when Cl- secretion-driven fluid secretion surpasses absorptive capacity. From a perspective of feedstuffs, factors that contribute to imbalances in fluid absorption and secretion in the intestines of weaned piglets include high levels of crude protein (CP), stimulation by certain antigenic proteins, high acid-binding capacity (ABC), and contamination with deoxynivalenol (DON) in the diet. In response, efforts to reduce CP levels in diets, select feedstuffs with lower ABC values, and process feedstuffs using physical, chemical, and biological approaches are important strategies for alleviating PWD in piglets. Additionally, the diet supplementation with additives such as vitamins and natural products can also play a role in reducing the diarrhea incidence in weaned piglets. Here, we examine the mechanisms of absorption and secretion of intestinal fluids and electrolytes in piglets, summarize nutritional strategies to control PWD in piglets from the perspective of feeds, and provide new insights towards future research directions.
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Affiliation(s)
- Qingsong Tang
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Tianyi Lan
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Chengyu Zhou
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Jingchun Gao
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Liuting Wu
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Haiyang Wei
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Wenxue Li
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Zhiru Tang
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Wenjie Tang
- Animal Breeding and Genetics Key Laboratory of Sichuan Province, Sichuan Animal Science Academy, Chengdu 610066, China
| | - Hui Diao
- Animal Breeding and Genetics Key Laboratory of Sichuan Province, Sichuan Animal Science Academy, Chengdu 610066, China
| | - Yetong Xu
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Xie Peng
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Jiaman Pang
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Xuan Zhao
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
| | - Zhihong Sun
- Laboratory for Bio-Feed and Molecular Nutrition, College of Animal Science and Technology, Southwest University, Chongqing 400715, China
- Yibin Academy of Southwest University, Yibin 644005, China
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2
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Liu J, Yan S, Du J, Teng L, Yang R, Xu P, Tao W. Mechanism and treatment of diarrhea associated with tyrosine kinase inhibitors. Heliyon 2024; 10:e27531. [PMID: 38501021 PMCID: PMC10945189 DOI: 10.1016/j.heliyon.2024.e27531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 02/29/2024] [Accepted: 03/01/2024] [Indexed: 03/20/2024] Open
Abstract
Tyrosine kinase inhibitors (TKIs) have become first-line drugs for cancer treatment. However, their clinical use is seriously hindered since many patients experience diarrhea after receiving TKIs. The mechanisms of TKI-associated diarrhea remain unclear. Most existing therapies are symptomatic treatments based on experience and their effects are unsatisfactory. Therefore, clarification of the mechanisms underlying diarrhea is critical to develop effective anti-diarrhea drugs. This article summarizes several potential mechanisms of TKI-associated diarrhea and reviews current treatment progress.
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Affiliation(s)
- Jiangnan Liu
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
| | - Shuai Yan
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- Key Laboratory of Hepatosplenic Surgery, Ministry of Education, Harbin, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
| | - Juntong Du
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
| | - Lizhi Teng
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
| | - Ru Yang
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
| | - Peng Xu
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
| | - Weiyang Tao
- Department of Breast Surgery, The First Affiliated Hospital of Harbin Medical University, Heilongjiang, 150001, PR China
- Key Laboratory of Acoustic, Optical and Electromagnetic Diagnosis and Treatment of Cardiovascular Diseases, Heilongjiang, 150001, PR China
- Key Laboratory of Hepatosplenic Surgery, Ministry of Education, Harbin, Heilongjiang, 150001, PR China
- The Cell Transplantation Key Laboratory of National Health Commission, Heilongjiang, 150001, PR China
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3
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Lu X, Luo C, Wu J, Deng Y, Mu X, Zhang T, Yang X, Liu Q, Li Z, Tang S, Hu Y, Du Q, Xu J, Xie R. Ion channels and transporters regulate nutrient absorption in health and disease. J Cell Mol Med 2023; 27:2631-2642. [PMID: 37638698 PMCID: PMC10494301 DOI: 10.1111/jcmm.17853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 07/03/2023] [Accepted: 07/06/2023] [Indexed: 08/29/2023] Open
Abstract
Ion channels and transporters are ubiquitously expressed on cell membrane, which involve in a plethora of physiological process such as contraction, neurotransmission, secretion and so on. Ion channels and transporters is of great importance to maintaining membrane potential homeostasis, which is essential to absorption of nutrients in gastrointestinal tract. Most of nutrients are electrogenic and require ion channels and transporters to absorb. This review summarizes the latest research on the role of ion channels and transporters in regulating nutrient uptake such as K+ channels, Ca2+ channels and ion exchangers. Revealing the mechanism of ion channels and transporters associated with nutrient uptake will be helpful to provide new methods to diagnosis and find potential targets for diseases like diabetes, inflammatory bowel diseases, etc. Even though some of study still remain ambiguous and in early stage, we believe that ion channels and transporters will be novel therapeutic targets in the future.
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Affiliation(s)
- Xianmin Lu
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Chen Luo
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Jiangbo Wu
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Ya Deng
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Xingyi Mu
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Ting Zhang
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Xiaoxu Yang
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Qi Liu
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Zhuo Li
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Siqi Tang
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Yanxia Hu
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Qian Du
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Jingyu Xu
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
| | - Rui Xie
- Department of GastroenterologyDigestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyiChina
- The Collaborative InnovAffiliated Hospital of Zunyi Medical Universityation Center of Tissue Damage Repair and Regeneration Medicine of Zunyi Medical UniversityZunyiChina
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4
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Thale I, Maskri S, Grey L, Todesca LM, Budde T, Maisuls I, Strassert CA, Koch O, Schwab A, Wünsch B. Imaging of K Ca 3.1 Channels in Tumor Cells with PET and Small-Molecule Fluorescent Probes. ChemMedChem 2023; 18:e202200551. [PMID: 36315933 PMCID: PMC10098740 DOI: 10.1002/cmdc.202200551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 10/31/2022] [Indexed: 01/20/2023]
Abstract
The Ca2+ activated K+ channel KCa 3.1 is overexpressed in several human tumor cell lines, e. g. clear cell renal carcinoma, prostate cancer, non-small cell lung cancer. Highly aggressive cancer cells use this ion channel for key processes of the metastatic cascade such as migration, extravasation and invasion. Therefore, small molecules, which are able to image this KCa 3.1 channel in vitro and in vivo represent valuable diagnostic and prognostic tool compounds. The [18 F]fluoroethyltriazolyl substituted senicapoc was used as positron emission tomography (PET) tracer and showed promising properties for imaging of KCa 3.1 channels in lung adenocarcinoma cells in mice. The novel senicapoc BODIPY conjugates with two F-atoms (9 a) and with a F-atom and a methoxy moiety (9 b) at the B-atom led to the characteristic punctate staining pattern resulting from labeling of single KCa 3.1 channels in A549-3R cells. This punctate pattern was completely removed by preincubation with an excess of senicapoc confirming the high specificity of KCa 3.1 labeling. Due to the methoxy moiety at the B-atom and the additional oxyethylene unit in the spacer, 9 b exhibits higher polarity, which improves solubility and handling without reduction of fluorescence quantum yield. Docking studies using a cryo-electron microscopy (EM) structure of the KCa 3.1 channel confirmed the interaction of 9 a and 9 b with a binding pocket in the channel pore.
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Affiliation(s)
- Insa Thale
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Institut für Pharmazeutische und Medizinische Chemie, Corrensstraße 48, 48149, Münster, Germany
| | - Sarah Maskri
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Institut für Pharmazeutische und Medizinische Chemie, Corrensstraße 48, 48149, Münster, Germany
| | - Lucie Grey
- Westfälische Wilhelms-Universität Münster, Institut für Pharmazeutische und Medizinische Chemie, Corrensstraße 48, 48149, Münster, Germany
| | - Luca Matteo Todesca
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Universitätsklinikum Münster, Institute of Physiology II, Robert-Koch-Straße 27b, 48149, Münster, Germany
| | - Thomas Budde
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Universitätsklinikum Münster, Institute of Physiology I, Robert-Koch-Straße 27a, 48149, Münster, Germany
| | - Ivan Maisuls
- Westfälische Wilhelms-Universität Münster, Institut für Anorganische und Analytische Chemie CiMIC, SoN, Corrensstraße 28, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, CeNTech, Heisenbergstraße 11, 48149, Münster, Germany
| | - Cristian A Strassert
- Westfälische Wilhelms-Universität Münster, Institut für Anorganische und Analytische Chemie CiMIC, SoN, Corrensstraße 28, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, CeNTech, Heisenbergstraße 11, 48149, Münster, Germany
| | - Oliver Koch
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Institut für Pharmazeutische und Medizinische Chemie, Corrensstraße 48, 48149, Münster, Germany
| | - Albrecht Schwab
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Universitätsklinikum Münster, Institute of Physiology II, Robert-Koch-Straße 27b, 48149, Münster, Germany
| | - Bernhard Wünsch
- Westfälische Wilhelms-Universität Münster, GRK 2515, Chemical biology of ion channels (Chembion), Corrensstraße 48, 48149, Münster, Germany.,Westfälische Wilhelms-Universität Münster, Institut für Pharmazeutische und Medizinische Chemie, Corrensstraße 48, 48149, Münster, Germany
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5
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Mehmood T, Pichyangkura R, Muanprasat C. Chitosan Oligosaccharide Prevents Afatinib-Induced Barrier Disruption and Chloride Secretion through Modulation of AMPK, PI3K/AKT, and ERK Signaling in T84 Cells. Polymers (Basel) 2022; 14:polym14204255. [PMID: 36297833 PMCID: PMC9611671 DOI: 10.3390/polym14204255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/26/2022] [Accepted: 09/29/2022] [Indexed: 12/03/2022] Open
Abstract
Diarrhea is an important adverse effect of epidermal growth factor receptor-tyrosine kinase inhibitors, especially afatinib. Novel antidiarrheal agents are needed to reduce epidermal growth factor receptor-tyrosine kinase inhibitor-associated diarrhea to improve the quality of life and treatment outcome in cancer patients. This study aimed to investigate the anti-diarrheal activity of chitosan oligosaccharide against afatinib-induced barrier disruption and chloride secretion in human intestinal epithelial cells (T84 cells). Chitosan oligosaccharide (100 μg/mL) prevented afatinib-induced barrier disruption determined by changes in transepithelial electrical resistance and FITC-dextran flux in the T84 cell monolayers. In addition, chitosan oligosaccharide prevented afatinib-induced potentiation of cAMP-induced chloride secretion measured by short-circuit current analyses in the T84 cell monolayers. Chitosan oligosaccharide induced the activation of AMPK, a positive regulator of epithelial tight junction and a negative regulator of cAMP-induced chloride secretion. Moreover, chitosan oligosaccharide partially reversed afatinib-induced AKT inhibition without affecting afatinib-induced ERK inhibition via AMPK-independent mechanisms. Collectively, this study reveals that chitosan oligosaccharide prevents the afatinib-induced diarrheal activities in T84 cells via both AMPK-dependent and AMPK-independent mechanisms. Chitosan oligosaccharide represents a promising natural polymer-derived compound for further development of treatment for afatinib-associated diarrheas.
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Affiliation(s)
- Tahir Mehmood
- Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bang Phli, Samut Prakan 10540, Thailand
| | - Rath Pichyangkura
- Department of Biochemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10400, Thailand
| | - Chatchai Muanprasat
- Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bang Phli, Samut Prakan 10540, Thailand
- Correspondence:
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7
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Du C, Chen S, Wan H, Chen L, Li L, Guo H, Tuo B, Dong H. Different functional roles for K + channel subtypes in regulating small intestinal glucose and ion transport. Biol Open 2019; 8:bio.042200. [PMID: 31243019 PMCID: PMC6679390 DOI: 10.1242/bio.042200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Although K+ channels are important in mediating the driving force for colonic ion transport, their role in small intestinal transport is poorly understood. To investigate this, small intestinal short circuit currents (Isc ) and HCO3 - secretion were measured in mice, and intracellular pH (pHi) was measured in small intestinal epithelial SCBN cells. The expression and location of Kv subtypes were verified by RT-PCR, western blotting and immunohistochemistry. Diabetic mice were also used to investigate the role of Kv subtypes in regulating intestinal glucose absorption. We found that KV7.1 is not involved in duodenal ion transport, while KCa3.1 selectively regulates duodenal Isc and HCO3 - secretion in a Ca2+-mediated but not cAMP-mediated manner. Blockade of KCa3.1 increased the rate of HCO3 - fluxes via cystic fibrosis transmembrane conductance regulator (CFTR) channels in SCBN cells. Jejunal Isc was significantly stimulated by glucose, but markedly inhibited by 4-aminopyridine (4-AP) and tetraethylammonium (TEA). Moreover, both Kv1.1 and Kv1.3 were expressed in jejunal mucosae. Finally, 4-AP significantly attenuated weight gain of normal and diabetic mice, and both 4-AP and TEA significantly lowered blood glucose of diabetic mice. This study not only examines the contribution of various K+ channel subtypes to small intestinal epithelial ion transport and glucose absorption, but also proposes a novel concept for developing specific K+ channel blockers to reduce weight gain and lower blood glucose in diabetes mellitus.
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Affiliation(s)
- Chao Du
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China.,Department of Gastroenterology and Hepatology, Chengdu Military General Hospital, Sichuan Province, Chengdu 610000, China
| | - Siyuan Chen
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China
| | - Hanxing Wan
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China
| | - Lihong Chen
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, and Digestive Disease Institute of Guizhou Province, Zunyi 563003, China
| | - Lingyu Li
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, and Digestive Disease Institute of Guizhou Province, Zunyi 563003, China
| | - Hong Guo
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, and Digestive Disease Institute of Guizhou Province, Zunyi 563003, China
| | - Hui Dong
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China .,Department of Medicine, School of Medicine, University of California, San Diego, CA 92093, USA
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8
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Rao MC. Physiology of Electrolyte Transport in the Gut: Implications for Disease. Compr Physiol 2019; 9:947-1023. [PMID: 31187895 DOI: 10.1002/cphy.c180011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We now have an increased understanding of the genetics, cell biology, and physiology of electrolyte transport processes in the mammalian intestine, due to the availability of sophisticated methodologies ranging from genome wide association studies to CRISPR-CAS technology, stem cell-derived organoids, 3D microscopy, electron cryomicroscopy, single cell RNA sequencing, transgenic methodologies, and tools to manipulate cellular processes at a molecular level. This knowledge has simultaneously underscored the complexity of biological systems and the interdependence of multiple regulatory systems. In addition to the plethora of mammalian neurohumoral factors and their cross talk, advances in pyrosequencing and metagenomic analyses have highlighted the relevance of the microbiome to intestinal regulation. This article provides an overview of our current understanding of electrolyte transport processes in the small and large intestine, their regulation in health and how dysregulation at multiple levels can result in disease. Intestinal electrolyte transport is a balance of ion secretory and ion absorptive processes, all exquisitely dependent on the basolateral Na+ /K+ ATPase; when this balance goes awry, it can result in diarrhea or in constipation. The key transporters involved in secretion are the apical membrane Cl- channels and the basolateral Na+ -K+ -2Cl- cotransporter, NKCC1 and K+ channels. Absorption chiefly involves apical membrane Na+ /H+ exchangers and Cl- /HCO3 - exchangers in the small intestine and proximal colon and Na+ channels in the distal colon. Key examples of our current understanding of infectious, inflammatory, and genetic diarrheal diseases and of constipation are provided. © 2019 American Physiological Society. Compr Physiol 9:947-1023, 2019.
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Affiliation(s)
- Mrinalini C Rao
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA
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9
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Duan T, Cil O, Thiagarajah JR, Verkman AS. Intestinal epithelial potassium channels and CFTR chloride channels activated in ErbB tyrosine kinase inhibitor diarrhea. JCI Insight 2019; 4:126444. [PMID: 30668547 PMCID: PMC6478423 DOI: 10.1172/jci.insight.126444] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 01/14/2019] [Indexed: 12/11/2022] Open
Abstract
Diarrhea is a major side effect of ErbB receptor tyrosine kinase inhibitors (TKIs) in cancer chemotherapy. Here, we show that the primary mechanism of ErbB TKI diarrhea is activation of basolateral membrane potassium (K+) channels and apical membrane chloride (Cl-) channels in intestinal epithelia and demonstrate the efficacy of channel blockers in a rat model of TKI diarrhea. Short-circuit current in colonic epithelial cells showed that the TKIs gefitinib, lapatinib, and afatinib do not affect basal secretion but amplify carbachol-stimulated secretion by 2- to 3-fold. Mechanistic studies with the second-generation TKI afatinib showed that the amplifying effect on Cl- secretion was Ca2+ and cAMP independent, was blocked by CF transmembrane conductance regulator (CFTR) and K+ channel inhibitors, and involved EGFR binding and ERK signaling. Afatinib-amplified activation of basolateral K+ and apical Cl- channels was demonstrated by selective membrane permeabilization, ion substitution, and channel inhibitors. Rats that were administered afatinib orally at 60 mg/kg/day developed diarrhea with increased stool water from approximately 60% to greater than 80%, which was reduced by up to 75% by the K+ channel inhibitors clotrimazole or senicapoc or the CFTR inhibitor (R)-BPO-27. These results indicate a mechanism for TKI diarrhea involving K+ and Cl- channel activation and support the therapeutic efficacy of channel inhibitors.
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Affiliation(s)
- Tianying Duan
- Departments of Medicine and Physiology, UCSF, San Francisco, California, USA.,Department of Gastroenterology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Onur Cil
- Departments of Medicine and Physiology, UCSF, San Francisco, California, USA.,Department of Pediatrics, UCSF, San Francisco, California, USA
| | - Jay R Thiagarajah
- Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, Massachusetts, USA.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, UCSF, San Francisco, California, USA
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10
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Zomer-van Ommen DD, de Poel E, Kruisselbrink E, Oppelaar H, Vonk AM, Janssens HM, van der Ent CK, Hagemeijer MC, Beekman JM. Comparison of ex vivo and in vitro intestinal cystic fibrosis models to measure CFTR-dependent ion channel activity. J Cyst Fibros 2018; 17:316-324. [PMID: 29544685 DOI: 10.1016/j.jcf.2018.02.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 01/15/2018] [Accepted: 02/06/2018] [Indexed: 12/23/2022]
Abstract
BACKGROUND New functional assays using primary human intestinal adult stem cell cultures can be valuable tools to study epithelial defects in human diseases such as cystic fibrosis. METHODS CFTR-mediated ion transport was measured in rectal organoid-derived monolayers grown from subjects with various CFTR mutations and compared to donor-matched intestinal current measurements (ICM) in rectal biopsies and forskolin-induced swelling of rectal organoids. RESULTS Rectal organoid-derived monolayers were generated within four days. Ion transport measurements of CFTR function using these monolayers correlated with ICM and organoid swelling (r = 0.73 and 0.79 respectively). Culturing the monolayers under differentiation conditions enhanced the detection of mucus-secreting cells and was accompanied by reduced CFTR function. CONCLUSIONS CFTR-dependent intestinal epithelial ion transport properties can be measured in rectal organoid-derived monolayers of subjects and correlate with donor-matched ICM and rectal organoid swelling.
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Affiliation(s)
- Domenique D Zomer-van Ommen
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Eyleen de Poel
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Evelien Kruisselbrink
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Hugo Oppelaar
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Annelotte M Vonk
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Hettie M Janssens
- Department of Pediatric Pulmonology, Erasmus Medical Centre, Sophia Children's Hospital, Rotterdam, The Netherlands
| | - Cornelis K van der Ent
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Marne C Hagemeijer
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Jeffrey M Beekman
- Department of Pediatric Pulmonology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, University Medical Centre Utrecht, Utrecht, The Netherlands.
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11
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Julio-Kalajzić F, Villanueva S, Burgos J, Ojeda M, Cid LP, Jentsch TJ, Sepúlveda FV. K 2P TASK-2 and KCNQ1-KCNE3 K + channels are major players contributing to intestinal anion and fluid secretion. J Physiol 2017; 596:393-407. [PMID: 29143340 DOI: 10.1113/jp275178] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 11/08/2017] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS K+ channels are important in intestinal epithelium as they ensure the ionic homeostasis and electrical potential of epithelial cells during anion and fluid secretion. Intestinal epithelium cAMP-activated anion secretion depends on the activity of the (also cAMP dependent) KCNQ1-KCNE3 K+ channel, but the secretory process survives after genetic inactivation of the K+ channel in the mouse. Here we use double mutant mice to investigate which alternative K+ channels come into action to compensate for the absence of KCNQ1-KCNE3 K+ channels. Our data establish that whilst Ca2+ -activated KCa 3.1 channels are not involved, K2P two-pore domain TASK-2 K+ channels are major players providing an alternative conductance to sustain the intestinal secretory process. Work with double mutant mice lacking both TASK-2 and KCNQ1-KCNE3 channels nevertheless points to yet-unidentified K+ channels that contribute to the robustness of the cAMP-activated anion secretion process. ABSTRACT Anion and fluid secretion across the intestinal epithelium, a process altered in cystic fibrosis and secretory diarrhoea, is mediated by cAMP-activated CFTR Cl- channels and requires the simultaneous activity of basolateral K+ channels to maintain cellular ionic homeostasis and membrane potential. This function is fulfilled by the cAMP-activated K+ channel formed by the association of pore-forming KCNQ1 with its obligatory KCNE3 β-subunit. Studies using mice show sizeable cAMP-activated intestinal anion secretion in the absence of either KCNQ1 or KCNE3 suggesting that an alternative K+ conductance must compensate for the loss of KCNQ1-KCNE3 activity. We used double mutant mouse and pharmacological approaches to identify such a conductance. Ca2+ -dependent anion secretion can also be supported by Ca2+ -dependent KCa 3.1 channels after independent CFTR activation, but cAMP-dependent anion secretion is not further decreased in the combined absence of KCa 3.1 and KCNQ1-KCNE3 K+ channel activity. We show that the K2P K+ channel TASK-2 is expressed in the epithelium of the small and large intestine. Tetrapentylammonium, a TASK-2 inhibitor, abolishes anion secretory current remaining in the absence of KCNQ1-KCNE3 activity. A double mutant mouse lacking both KCNQ1-KCNE3 and TASK-2 showed a much reduced cAMP-mediated anion secretion compared to that observed in the single KCNQ1-KCNE3 deficient mouse. We conclude that KCNQ1-KCNE3 and TASK-2 play major roles in the intestinal anion and fluid secretory phenotype. The persistence of an, admittedly reduced, secretory activity in the absence of these two conductances suggests that further additional K+ channel(s) as yet unidentified contribute to the robustness of the intestinal anion secretory process.
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Affiliation(s)
| | - Sandra Villanueva
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Johanna Burgos
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile.,Universidad Austral de Chile, Valdivia, Chile
| | - Margarita Ojeda
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - L Pablo Cid
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, Valdivia, Chile
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
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12
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Han J, Lee SH, Giebisch G, Wang T. Potassium Channelopathies and Gastrointestinal Ulceration. Gut Liver 2017; 10:881-889. [PMID: 27784845 PMCID: PMC5087926 DOI: 10.5009/gnl15414] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/14/2015] [Accepted: 10/20/2015] [Indexed: 12/13/2022] Open
Abstract
Potassium channels and transporters maintain potassium homeostasis and play significant roles in several different biological actions via potassium ion regulation. In previous decades, the key revelations that potassium channels and transporters are involved in the production of gastric acid and the regulation of secretion in the stomach have been recognized. Drugs used to treat peptic ulceration are often potassium transporter inhibitors. It has also been reported that potassium channels are involved in ulcerative colitis. Direct toxicity to the intestines from nonsteroidal anti-inflammatory drugs has been associated with altered potassium channel activities. Several reports have indicated that the long-term use of the antianginal drug Nicorandil, an adenosine triphosphate-sensitive potassium channel opener, increases the chances of ulceration and perforation from the oral to anal regions throughout the gastrointestinal (GI) tract. Several of these drug features provide further insights into the role of potassium channels in the occurrence of ulceration in the GI tract. The purpose of this review is to investigate whether potassium channelopathies are involved in the mechanisms responsible for ulceration that occurs throughout the GI tract.
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Affiliation(s)
- Jaeyong Han
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
| | - Seung Hun Lee
- Department of Internal Medicine, Section of Nephrology, Yale University, New Haven, CT, USA
| | - Gerhard Giebisch
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
| | - Tong Wang
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
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13
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Pongkorpsakol P, Yimnual C, Chatsudthipong V, Rukachaisirikul V, Muanprasat C. Cellular mechanisms underlying the inhibitory effect of flufenamic acid on chloride secretion in human intestinal epithelial cells. J Pharmacol Sci 2017; 134:93-100. [PMID: 28651800 DOI: 10.1016/j.jphs.2017.05.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/09/2017] [Accepted: 05/19/2017] [Indexed: 01/10/2023] Open
Abstract
Intestinal Cl- secretion is involved in the pathogenesis of secretory diarrheas including cholera. We recently demonstrated that flufenamic acid (FFA) suppressed Vibrio cholerae El Tor variant-induced intestinal fluid secretion via mechanisms involving AMPK activation and NF-κB-suppression. The present study aimed to investigate the effect of FFA on transepithelial Cl- secretion in human intestinal epithelial (T84) cells. FFA inhibited cAMP-dependent Cl- secretion in T84 cell monolayers with IC50 of ∼8 μM. Other fenamate drugs including tolfenamic acid, meclofenamic acid and mefenamic acid exhibited the same effect albeit with lower potency. FFA also inhibited activities of CFTR, a cAMP-activated apical Cl- channel, and KCNQ1/KCNE3, a cAMP-activated basolateral K+ channel. Mechanisms of CFTR inhibition by FFA did not involve activation of its negative regulators. Interestingly, FFA inhibited Ca2+-dependent Cl- secretion with IC50 of ∼10 μM. FFA inhibited activities of Ca2+-activated Cl- channels and KCa3.1, a Ca2+-activated basolateral K+ channels, but had no effect on activities of Na+-K+-Cl- cotransporters and Na+-K+ ATPases. These results indicate that FFA inhibits both cAMP and Ca2+-dependent Cl- secretion by suppressing activities of both apical Cl- channels and basolateral K+ channels. FFA and other fenamate drugs may be useful in the treatment of secretory diarrheas.
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Affiliation(s)
- Pawin Pongkorpsakol
- Translational Medicine Graduate Program, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand
| | - Chantapol Yimnual
- Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand
| | - Varanuj Chatsudthipong
- Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand
| | - Vatcharin Rukachaisirikul
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand
| | - Chatchai Muanprasat
- Department of Physiology, Faculty of Science, Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand; Excellent Center for Drug Discovery (ECDD), Mahidol University, Rama VI Road, Rajathevi, Bangkok 10400, Thailand.
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14
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Sevelsted Møller L, Fialla AD, Schierwagen R, Biagini M, Liedtke C, Laleman W, Klein S, Reul W, Koch Hansen L, Rabjerg M, Singh V, Surra J, Osada J, Reinehr R, de Muckadell OBS, Köhler R, Trebicka J. The calcium-activated potassium channel KCa3.1 is an important modulator of hepatic injury. Sci Rep 2016; 6:28770. [PMID: 27354175 PMCID: PMC4926059 DOI: 10.1038/srep28770] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 06/10/2016] [Indexed: 12/12/2022] Open
Abstract
The calcium-activated potassium channel KCa3.1 controls different cellular processes such as proliferation and volume homeostasis. We investigated the role of KCa3.1 in experimental and human liver fibrosis. KCa3.1 gene expression was investigated in healthy and injured human and rodent liver. Effect of genetic depletion and pharmacological inhibition of KCa3.1 was evaluated in mice during carbon tetrachloride induced hepatic fibrogenesis. Transcription, protein expression and localisation of KCa3.1 was analysed by reverse transcription polymerase chain reaction, Western blot and immunohistochemistry. Hemodynamic effects of KCa3.1 inhibition were investigated in bile duct-ligated and carbon tetrachloride intoxicated rats. In vitro experiments were performed in rat hepatic stellate cells and hepatocytes. KCa3.1 expression was increased in rodent and human liver fibrosis and was predominantly observed in the hepatocytes. Inhibition of KCa3.1 aggravated liver fibrosis during carbon tetrachloride challenge but did not change hemodynamic parameters in portal hypertensive rats. In vitro, KCa3.1 inhibition leads to increased hepatocyte apoptosis and DNA damage, whereas proliferation of hepatic stellate cells was stimulated by KCa3.1 inhibition. Our data identifies KCa3.1 channels as important modulators in hepatocellular homeostasis. In contrast to previous studies in vitro and other tissues this channel appears to be anti-fibrotic and protective during liver injury.
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Affiliation(s)
- Linda Sevelsted Møller
- Department of Medical Gastroenterology and Hepatology, Odense University Hospital, Odense, Denmark.,Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Annette Dam Fialla
- Department of Medical Gastroenterology and Hepatology, Odense University Hospital, Odense, Denmark
| | | | - Matteo Biagini
- Department of Pathology, Odense University Hospital, Odense, Denmark
| | - Christian Liedtke
- Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany
| | - Wim Laleman
- Department of Liver and Biliopancreatic disorders, University of Leuven, Leuven, Belgium
| | - Sabine Klein
- Department of Internal Medicine I, University of Bonn, Bonn, Germany
| | - Winfried Reul
- Department of Internal Medicine I, University of Bonn, Bonn, Germany
| | - Lars Koch Hansen
- Department of Medical Gastroenterology and Hepatology, Vejle Hospital, Vejle, Denmark
| | - Maj Rabjerg
- Department of Pathology, Odense University Hospital, Odense, Denmark
| | - Vikrant Singh
- Department of Pharmacology, University of California, Davis, California, USA
| | - Joaquin Surra
- Departament de Producción Animal, Escuela Politécnica Superior, Huesca, Spain
| | - Jesus Osada
- Departamento Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón (IIS), Universidad de Zaragoza-CIBEROBN, Zaragoza, Spain
| | - Roland Reinehr
- Elbe-Elster Klinikum, Krankenhaus Herzberg, Herzberg, Germany
| | | | - Ralf Köhler
- Aragon Institute of Health Science I CS, Zaragoza, Spain
| | - Jonel Trebicka
- Department of Medical Gastroenterology and Hepatology, Odense University Hospital, Odense, Denmark.,Department of Internal Medicine I, University of Bonn, Bonn, Germany
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15
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Al-Hazza A, Linley J, Aziz Q, Hunter M, Sandle G. Upregulation of basolateral small conductance potassium channels (KCNQ1/KCNE3) in ulcerative colitis. Biochem Biophys Res Commun 2015; 470:473-478. [PMID: 26718405 PMCID: PMC4748010 DOI: 10.1016/j.bbrc.2015.12.086] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 12/20/2015] [Indexed: 12/04/2022]
Abstract
Background Basolateral K+ channels hyperpolarize colonocytes to ensure Na+ (and thus water) absorption. Small conductance basolateral (KCNQ1/KCNE3) K+ channels have never been evaluated in human colon. We therefore evaluated KCNQ1/KCNE3 channels in distal colonic crypts obtained from normal and active ulcerative colitis (UC) patients. Methods KCNQ1 and KCNE3 mRNA levels were determined by qPCR, and KCNQ1/KCNE3 channel activity in normal and UC crypts, and the effects of forskolin (activator of adenylate cyclase) and UC-related proinflammatory cytokines on normal crypts, studied by patch clamp recording. Results Whereas KCNQ1 and KCNE3 mRNA expression was similar in normal and UC crypts, single 6.8 pS channels were seen in 36% of basolateral patches in normal crypts, and to an even greater extent (74% of patches, P < 0.001) in UC crypts, with two or more channels per patch. Channel activity was 10-fold higher (P < 0.001) in UC crypts, with a greater contribution to basolateral conductance (5.85 ± 0.62 mS cm−2) than in controls (0.28 ± 0.04 mS cm−2, P < 0.001). In control crypts, forskolin and thromboxane A2 stimulated channel activity 30-fold and 10-fold respectively, while PGE2, IL-1β, and LTD4 had no effect. Conclusions KCNQ1/KCNE3 channels make only a small contribution to basolateral conductance in normal colonic crypts, with increased channel activity in UC appearing insufficient to prevent colonic cell depolarization in this disease. This supports the proposal that defective Na+ absorption rather than enhanced Cl− secretion, is the dominant pathophysiological mechanism of diarrhea in UC.
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Affiliation(s)
- Adel Al-Hazza
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - John Linley
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - Qadeer Aziz
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - Malcolm Hunter
- Institute of Membrane and Systems Biology, University of Leeds, UK
| | - Geoffrey Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St. James's University Hospital, Leeds, UK.
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16
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Nichols JM, Maiellaro I, Abi-Jaoude J, Curci S, Hofer AM. "Store-operated" cAMP signaling contributes to Ca2+-activated Cl- secretion in T84 colonic cells. Am J Physiol Gastrointest Liver Physiol 2015; 309:G670-9. [PMID: 26316590 PMCID: PMC4609931 DOI: 10.1152/ajpgi.00214.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/21/2015] [Indexed: 01/31/2023]
Abstract
Apical cAMP-dependent CFTR Cl(-) channels are essential for efficient vectorial movement of ions and fluid into the lumen of the colon. It is well known that Ca(2+)-mobilizing agonists also stimulate colonic anion secretion. However, CFTR is apparently not activated directly by Ca(2+), and the existence of apical Ca(2+)-dependent Cl(-) channels in the native colonic epithelium is controversial, leaving the identity of the Ca(2+)-activated component unresolved. We recently showed that decreasing free Ca(2+) concentration ([Ca(2+)]) within the endoplasmic reticulum (ER) lumen elicits a rise in intracellular cAMP. This process, which we termed "store-operated cAMP signaling" (SOcAMPS), requires the luminal ER Ca(2+) sensor STIM1 and does not depend on changes in cytosolic Ca(2+). Here we assessed the degree to which SOcAMPS participates in Ca(2+)-activated Cl(-) transport as measured by transepithelial short-circuit current (Isc) in polarized T84 monolayers in parallel with imaging of cAMP and PKA activity using fluorescence resonance energy transfer (FRET)-based reporters in single cells. In Ca(2+)-free conditions, the Ca(2+)-releasing agonist carbachol and Ca(2+) ionophore increased Isc, cAMP, and PKA activity. These responses persisted in cells loaded with the Ca(2+) chelator BAPTA-AM. The effect on Isc was enhanced in the presence of the phosphodiesterase (PDE) inhibitor 3-isobutyl-1-methylxanthine (IBMX), inhibited by the CFTR inhibitor CFTRinh-172 and the PKA inhibitor H-89, and unaffected by Ba(2+) or flufenamic acid. We propose that a discrete component of the "Ca(2+)-dependent" secretory activity in the colon derives from cAMP generated through SOcAMPS. This alternative mode of cAMP production could contribute to the actions of diverse xenobiotic agents that disrupt ER Ca(2+) homeostasis, leading to diarrhea.
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Affiliation(s)
- Jonathan M. Nichols
- Department of Veterans Affairs Boston Healthcare System and Department of Surgery, Brigham & Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts
| | - Isabella Maiellaro
- Department of Veterans Affairs Boston Healthcare System and Department of Surgery, Brigham & Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts
| | - Joanne Abi-Jaoude
- Department of Veterans Affairs Boston Healthcare System and Department of Surgery, Brigham & Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts
| | - Silvana Curci
- Department of Veterans Affairs Boston Healthcare System and Department of Surgery, Brigham & Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts
| | - Aldebaran M. Hofer
- Department of Veterans Affairs Boston Healthcare System and Department of Surgery, Brigham & Women's Hospital and Harvard Medical School, West Roxbury, Massachusetts
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17
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Abstract
Diarrhoeal disease remains a major health burden worldwide. Secretory diarrhoeas are caused by certain bacterial and viral infections, inflammatory processes, drugs and genetic disorders. Fluid secretion across the intestinal epithelium in secretory diarrhoeas involves multiple ion and solute transporters, as well as activation of cyclic nucleotide and Ca(2+) signalling pathways. In many secretory diarrhoeas, activation of Cl(-) channels in the apical membrane of enterocytes, including the cystic fibrosis transmembrane conductance regulator and Ca(2+)-activated Cl(-) channels, increases fluid secretion, while inhibition of Na(+) transport reduces fluid absorption. Current treatment of diarrhoea includes replacement of fluid and electrolyte losses using oral rehydration solutions, and drugs targeting intestinal motility or fluid secretion. Therapeutics in the development pipeline target intestinal ion channels and transporters, regulatory proteins and cell surface receptors. This Review describes pathogenic mechanisms of secretory diarrhoea, current and emerging therapeutics, and the challenges in developing antidiarrhoeal therapeutics.
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Affiliation(s)
- Jay R Thiagarajah
- Division of Gastroenterology, Hepatology and Nutrition, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
| | - Mark Donowitz
- Departments of Physiology and Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Ross 925, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, 1246 Health Sciences East Tower, University of California, 500 Parnassus Avenue, San Francisco, CA 94143, USA
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18
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Expression of T-cell KV1.3 potassium channel correlates with pro-inflammatory cytokines and disease activity in ulcerative colitis. J Crohns Colitis 2014; 8:1378-91. [PMID: 24793818 PMCID: PMC4216648 DOI: 10.1016/j.crohns.2014.04.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 03/18/2014] [Accepted: 04/07/2014] [Indexed: 02/08/2023]
Abstract
BACKGROUND AND AIMS Potassium channels, KV1.3 and KCa3.1, have been suggested to control T-cell activation, proliferation, and cytokine production and may thus constitute targets for anti-inflammatory therapy. Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by excessive T-cell infiltration and cytokine production. It is unknown if KV1.3 and KCa3.1 in the inflamed mucosa are markers of active UC. We hypothesized that KV1.3 and KCa3.1 correlate with disease activity and cytokine production in patients with UC. METHODS Mucosal biopsies were collected from patients with active UC (n=33) and controls (n=15). Protein and mRNA expression of KV1.3 and KCa3.1, immune cell markers, and pro-inflammatory cytokines were determined by quantitative-real-time-polymerase-chain-reaction (qPCR) and immunofluorescence, and correlated with clinical parameters of inflammation. In-vitro cytokine production was measured in human CD3(+) T-cells after pharmacological blockade of KV1.3 and KCa3.1. RESULTS Active UC KV1.3 mRNA expression was increased 5-fold compared to controls. Immunofluorescence analyses revealed that KV1.3 protein was present in inflamed mucosa in 57% of CD4(+) and 23% of CD8(+) T-cells. KV1.3 was virtually absent on infiltrating macrophages. KV1.3 mRNA expression correlated significantly with mRNA expression of pro-inflammatory cytokines TNF-α (R(2)=0.61) and IL-17A (R(2)=0.51), the mayo endoscopic subscore (R(2)=0.13), and histological inflammation (R(2)=0.23). In-vitro blockade of T-cell KV1.3 and KCa3.1 decreased production of IFN-γ, TNF-α, and IL-17A. CONCLUSIONS High levels of KV1.3 in CD4 and CD8 positive T-cells infiltrates are associated with production of pro-inflammatory IL-17A and TNF-α in active UC. KV1.3 may serve as a marker of disease activity and pharmacological blockade might constitute a novel immunosuppressive strategy.
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19
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Sheikh IA, Koley H, Chakrabarti MK, Hoque KM. The Epac1 signaling pathway regulates Cl- secretion via modulation of apical KCNN4c channels in diarrhea. J Biol Chem 2013; 288:20404-15. [PMID: 23720748 DOI: 10.1074/jbc.m113.467860] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The apical membrane of intestinal epithelia expresses intermediate conductance K(+) channel (KCNN4), which provides the driving force for Cl(-) secretion. However, its role in diarrhea and regulation by Epac1 is unknown. Previously we have established that Epac1 upon binding of cAMP activates a PKA-independent mechanism of Cl(-) secretion via stimulation of Rap2-phospholipase Cε-[Ca(2+)]i signaling. Here we report that Epac1 regulates surface expression of KCNN4c channel through its downstream Rap1A-RhoA-Rho-associated kinase (ROCK) signaling pathway for sustained Cl(-) secretion. Depletion of Epac1 protein and apical addition of TRAM-34, a specific KCNN4 inhibitor, significantly abolished cAMP-stimulated Cl(-) secretion and apical K(+) conductance (IK(ap)) in T84WT cells. The current-voltage relationship of basolaterally permeabilized monolayers treated with Epac1 agonist 8-(4-chlorophenylthio)-2'-O- methyladenosine 3',5'-cyclic monophosphate showed the presence of an inwardly rectifying and TRAM-34-sensitive K(+) channel in T84WT cells that was absent in Epac1KDT84 cells. Reconstructed confocal images in Epac1KDT84 cells revealed redistribution of KCNN4c proteins into subapical intracellular compartment, and a biotinylation assay showed ∼83% lower surface expression of KCNN4c proteins compared with T84WT cells. Further investigation revealed that an Epac1 agonist activates Rap1 to facilitate IK(ap). Both RhoA inhibitor (GGTI298) and ROCK inhibitor (H1152) significantly reduced cAMP agonist-stimulated IK(ap), whereas the latter additionally reduced colocalization of KCNN4c with the apical membrane marker wheat germ agglutinin in T84WT cells. In vivo mouse ileal loop experiments showed reduced fluid accumulation by TRAM-34, GGTI298, or H1152 when injected together with cholera toxin into the loop. We conclude that Rap1A-dependent signaling of Epac1 involving RhoA-ROCK is an important regulator of intestinal fluid transport via modulation of apical KCNN4c channels, a finding with potential therapeutic value in diarrheal diseases.
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Affiliation(s)
- Irshad Ali Sheikh
- Division of Molecular Pathophysiology, National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme-XM, Beliaghata, Kolkata 700010, India
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20
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KCNN4 channels participate in the EMT induced by PRL-3 in colorectal cancer. Med Oncol 2013; 30:566. [PMID: 23572150 DOI: 10.1007/s12032-013-0566-z] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 03/30/2013] [Indexed: 02/08/2023]
Abstract
Studies have shown that phosphatase of regenerating liver-3 (PRL-3) promotes the invasion, migration, and metastasis of human tumor cells by facilitating an epithelial-mesenchymal transition (EMT). However, the mechanism by which PRL-3 induces tumor cell EMT is unknown. Our previous research revealed that PRL-3 promotes LoVo cell proliferation by up-regulating KCNN4 channels. In the current study, we explored the mechanism by which PRL-3 mediates EMT. We demonstrated that PRL-3 induced the expression of KCNN4 channels, leading to EMT and the down-regulation of E-cadherin. Further studies revealed that KCNN4 channels increased intracellular calcium levels and activated components of cell signaling downstream of calcium, including CaM-kinase II and glycogen synthase kinase-3 beta (GSK-3 beta), which increased Snail expression. Inhibiting KCNN4 with siRNA and TRAM-34, a specific inhibitor, restored E-cadherin expression and inhibited Snail expression. These results implicated the up-regulation of KCNN4 channels in the PRL-3-mediated induction of EMT and promotion of cancer metastasis.
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Zhang J, Halm ST, Halm DR. Role of the BK channel (KCa1.1) during activation of electrogenic K+ secretion in guinea pig distal colon. Am J Physiol Gastrointest Liver Physiol 2012; 303:G1322-34. [PMID: 23064759 PMCID: PMC3532550 DOI: 10.1152/ajpgi.00325.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Secretagogues acting at a variety of receptor types activate electrogenic K(+) secretion in guinea pig distal colon, often accompanied by Cl(-) secretion. Distinct blockers of K(Ca)1.1 (BK, Kcnma1), iberiotoxin (IbTx), and paxilline inhibited the negative short-circuit current (I(sc)) associated with K(+) secretion. Mucosal addition of IbTx inhibited epinephrine-activated I(sc) ((epi)I(sc)) and transepithelial conductance ((epi)G(t)) consistent with K(+) secretion occurring via apical membrane K(Ca)1.1. The concentration dependence of IbTx inhibition of (epi)I(sc) yielded an IC(50) of 193 nM, with a maximal inhibition of 51%. Similarly, IbTx inhibited (epi)G(t) with an IC(50) of 220 nM and maximal inhibition of 48%. Mucosally added paxilline (10 μM) inhibited (epi)I(sc) and (epi)G(t) by ∼50%. IbTx and paxilline also inhibited I(sc) activated by mucosal ATP, supporting apical K(Ca)1.1 as a requirement for this K(+) secretagogue. Responses to IbTx and paxilline indicated that a component of K(+) secretion occurred during activation of Cl(-) secretion by prostaglandin-E(2) and cholinergic stimulation. Analysis of K(Ca)1.1α mRNA expression in distal colonic epithelial cells indicated the presence of the ZERO splice variant and three splice variants for the COOH terminus. The presence of the regulatory β-subunits K(Ca)β1 and K(Ca)β4 also was demonstrated. Immunolocalization supported the presence of K(Ca)1.1α in apical and basolateral membranes of surface and crypt cells. Together these results support a cellular mechanism for electrogenic K(+) secretion involving apical membrane K(Ca)1.1 during activation by several secretagogue types, but the observed K(+) secretion likely required the activity of additional K(+) channel types in the apical membrane.
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Affiliation(s)
- Jin Zhang
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
| | - Susan T. Halm
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
| | - Dan R. Halm
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine, Dayton, Ohio
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22
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GUSTAFSSON JK, HANSSON GC, SJÖVALL H. Ulcerative colitis patients in remission have an altered secretory capacity in the proximal colon despite macroscopically normal mucosa. Neurogastroenterol Motil 2012; 24:e381-91. [PMID: 22726848 PMCID: PMC4871264 DOI: 10.1111/j.1365-2982.2012.01958.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND One of the hallmarks of acute colitis is loss of epithelial transport. For unknown reasons, many patients still suffer from GI symptoms during remission, indicating a sustained imbalance between absorption and secretion. We hypothesize that the colonic epithelium becomes more reactive to secretagogues to compensate for a failing barrier. METHODS Biopsies from ascending colon and sigmoid colon of UC patients in remission and controls were mounted in Ussing chambers. Membrane current (Im) and epithelial capacitance (Cp) were used as markers for anion secretion and mucus exocytosis. Carbachol (1 mmol L(-1) ) and forskolin (10 μmol L(-1) ) were used to study Ca(2+) and cAMP-mediated secretion. KEY RESULTS Baseline values showed segmental patterns with higher Im in ascending colon and higher Cp in sigmoid colon of both UC patients and controls, but the patterns did not differ between the groups. The Im response to forskolin was increased (+35%) in the ascending colon of UC patients and the Im response to carbachol was decreased (-40%) in the same segment. No group differences were seen in the distal colon for either the forskolin or carbachol-induced Im responses. The Cp response to carbachol was instead up-regulated in the distal colon of UC patients, but remained unaffected in the proximal colon. CONCLUSIONS & INFERENCES The proximal colonic mucosa of UC patients in remission seems to shift its reactivity to secretagogues, becoming more sensitive to cAMP-dependent secretion and less sensitive to Ca(2+) -dependent secretion. This phenomenon may contribute to residual diarrhea in this patient group, despite resolution of inflammation.
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Affiliation(s)
- J. K. GUSTAFSSON
- Department of Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden,Department of Medical Biochemistry and Cell Biology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - G. C. HANSSON
- Department of Medical Biochemistry and Cell Biology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - H. SJÖVALL
- Department of Internal Medicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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23
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Gustafsson JK, Ermund A, Johansson MEV, Schütte A, Hansson GC, Sjövall H. An ex vivo method for studying mucus formation, properties, and thickness in human colonic biopsies and mouse small and large intestinal explants. Am J Physiol Gastrointest Liver Physiol 2012; 302:G430-8. [PMID: 22159279 PMCID: PMC4073982 DOI: 10.1152/ajpgi.00405.2011] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The colon mucus layers minimize the contact between the luminal flora and the epithelial cells, and defects in this barrier may lead to colonic inflammation. We now describe an ex vivo method for analysis of mucus properties in human colon and mouse small and large intestine. Intestinal explants were mounted in horizontal perfusion chambers. The mucus surface was visualized by adding charcoal particles on the apical side, and mucus thickness was measured using a micropipette. Mucus thickness, adhesion, and growth rate were recorded for 1 h. In mouse and human colon, the ability of the mucus to act as a barrier to beads the size of bacteria was also evaluated. Tissue viability was monitored by transepithelial potential difference. In mouse ileum, the mucus could be removed by gentle aspiration, whereas in colon ∼40 μm of the mucus remained attached to the epithelial surface. Both mouse and human colon had an inner mucus layer that was not penetrated by the fluorescent beads. Spontaneous mucus growth was observed in human (240 μm/h) and mouse (100 μm/h) colon but not in mouse ileum. In contrast, stimulation with carbachol induced a higher mucus secretion in ileum than colon (mouse ileum: Δ200 μm, mouse colon: Δ130 μm, human colon: Δ140 μm). In conclusion, while retaining key properties from the mucus system in vivo, this setup also allows for studies of the highly dynamic mucus system under well-controlled conditions.
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Affiliation(s)
| | | | | | | | | | - Henrik Sjövall
- 3Internal Medicine, University of Gothenburg, Gothenburg, Sweden
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24
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Muanprasat C, Sirianant L, Soodvilai S, Chokchaisiri R, Suksamrarn A, Chatsudthipong V. Novel Action of the Chalcone Isoliquiritigenin as a Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Inhibitor: Potential Therapy for Cholera and Polycystic Kidney Disease. J Pharmacol Sci 2012; 118:82-91. [DOI: 10.1254/jphs.11153fp] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 11/10/2011] [Indexed: 10/14/2022] Open
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25
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Bekkali N, de Jonge HR, van den Wijngaard RMJGJ, van der Steeg AFW, Bijlsma PB, Taminiau JAJM, Desjeux JF, Benninga MA. The role of rectal chloride secretion in childhood constipation. Neurogastroenterol Motil 2011; 23:1007-12. [PMID: 21848627 DOI: 10.1111/j.1365-2982.2011.01751.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Disturbance in fluid secretion, driven by chloride secretion, might play a role in constipation. However, disturbed chloride secretion in those patients has yet to be evaluated. Therefore, the aim of this study was to compare chloride secretion in rectal biopsies of children with functional constipation (FC) to those without constipation. METHODS To measure changes in short circuit current (I(sc) in μA cm(-2)) reflecting chloride secretion, intestinal biopsies from children with constipation, to either exclude or diagnose Hirschsprung's disease, and from children without constipation (controls) undergoing colonoscopy for screening of familial adenomatous polyposis, juvenile polyps or inflammatory bowel disease (IBD), were compared and studied in Ussing chambers. Following electrogenic sodium absorption blockade by amiloride, chloride secretory responses to calcium-linked (histamine, carbachol) and cAMP-linked (IBMX/forskolin) secretagogues were assessed. KEY RESULTS Ninety-six patients (46 FC) participated; nine FC patients (n = 1 congenital syndrome and n = 8 technical problems) and 13 controls (n = 6 IBD; n = 7 technical problems) were excluded. No significant difference was found in mean (±SE) basal chloride currents between children with FC and controls (9.6 ± 1.1 vs 9.2 ± 0.8; P = 0.75, respectively). Responses to calcium-linked chloride secretagogues (histamine and carbachol) were significantly higher in controls (33.0 ± 3.0 vs 24.5 ± 2.3; P = 0.03 and 33.6 ± 3.4 vs 26.4 ± 2.7; P = 0.05 following histamine and carbachol, respectively). CONCLUSIONS & INFERENCES Calcium-linked chloride secretion is disturbed in children with FC. Whether this defect occurs at the level of histamine receptors, components of receptor-linked signal transduction pathways or basolateral Ca(2+) -sensitive K(+) channels enhancing the electrical driving force for apical chloride secretion, remains to be explored.
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Affiliation(s)
- N Bekkali
- Department of Paediatric Gastroenterology and Nutrition, Emma Children's Hospital, Amsterdam, The Netherlands.
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26
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Hock M, Soták M, Kment M, Pácha J. The early effect of dextran sodium sulfate administration on carbachol-induced short-circuit current in distal and proximal colon during colitis development. Physiol Res 2011; 60:921-31. [PMID: 21995894 DOI: 10.33549/physiolres.932222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Increased colonic Cl(-) secretion was supposed to be a causative factor of diarrhea in inflammatory bowel diseases. Surprisingly, hyporesponsiveness to Cl(-) secretagogues was later described in inflamed colon. Our aim was to evaluate changes in secretory responses to cholinergic agonist carbachol in distal and proximal colon during colitis development, regarding secretory activity of enteric nervous system (ENS) and prostaglandins. Increased responsiveness to carbachol was observed in both distal and proximal colon after 3 days of 2 % dextran sodium sulfate (DSS) administration. It was measured in the presence of mucosal Ba(2+) to emphasize Cl(-) secretion. The described increase was abolished by combined inhibitory effect of tetrodotoxin (TTX) and indomethacin. Indomethacin also significantly reduced TTX-sensitive current. On the 7th day of colitis development responsiveness to carbachol decreased in distal colon (compared to untreated mice), but did not change in proximal colon. TTX-sensitive current did not change during colitis development, but indomethacin-sensitive current was significantly increased the 7th day. Decreased and deformed current responses to serosal Ba(2+) were observed during colitis induction, but only in proximal colon. We conclude that besides inhibitory effect of DSS on distal colon responsiveness, there is an early stimulatory effect that manifests in both distal and proximal colon.
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Affiliation(s)
- M Hock
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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27
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Roth EK, Hirtz S, Duerr J, Wenning D, Eichler I, Seydewitz HH, Amaral MD, Mall MA. The K+ channel opener 1-EBIO potentiates residual function of mutant CFTR in rectal biopsies from cystic fibrosis patients. PLoS One 2011; 6:e24445. [PMID: 21909392 PMCID: PMC3164200 DOI: 10.1371/journal.pone.0024445] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Accepted: 08/10/2011] [Indexed: 12/05/2022] Open
Abstract
Background The identification of strategies to improve mutant CFTR function remains a key priority in the development of new treatments for cystic fibrosis (CF). Previous studies demonstrated that the K+ channel opener 1-ethyl-2-benzimidazolone (1-EBIO) potentiates CFTR-mediated Cl− secretion in cultured cells and mouse colon. However, the effects of 1-EBIO on wild-type and mutant CFTR function in native human colonic tissues remain unknown. Methods We studied the effects of 1-EBIO on CFTR-mediated Cl− secretion in rectal biopsies from 47 CF patients carrying a wide spectrum of CFTR mutations and 57 age-matched controls. Rectal tissues were mounted in perfused micro-Ussing chambers and the effects of 1-EBIO were compared in control tissues, CF tissues expressing residual CFTR function and CF tissues with no detectable Cl− secretion. Results Studies in control tissues demonstrate that 1-EBIO activated CFTR-mediated Cl− secretion in the absence of cAMP-mediated stimulation and potentiated cAMP-induced Cl− secretion by 39.2±6.7% (P<0.001) via activation of basolateral Ca2+-activated and clotrimazole-sensitive KCNN4 K+ channels. In CF specimens, 1-EBIO potentiated cAMP-induced Cl− secretion in tissues with residual CFTR function by 44.4±11.5% (P<0.001), but had no effect on tissues lacking CFTR-mediated Cl−conductance. Conclusions We conclude that 1-EBIO potentiates Cl−secretion in native CF tissues expressing CFTR mutants with residual Cl− channel function by activation of basolateral KCNN4 K+ channels that increase the driving force for luminal Cl− exit. This mechanism may augment effects of CFTR correctors and potentiators that increase the number and/or activity of mutant CFTR channels at the cell surface and suggests KCNN4 as a therapeutic target for CF.
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Affiliation(s)
- Eva K. Roth
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics III, University of Heidelberg, Heidelberg, Germany
- Translational Lung Research Center, University of Heidelberg, Heidelberg, Germany
| | - Stephanie Hirtz
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics III, University of Heidelberg, Heidelberg, Germany
- Translational Lung Research Center, University of Heidelberg, Heidelberg, Germany
| | - Julia Duerr
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics III, University of Heidelberg, Heidelberg, Germany
- Translational Lung Research Center, University of Heidelberg, Heidelberg, Germany
| | - Daniel Wenning
- Pediatric Gastroenterology and Hepatology, Department of Pediatrics I, University of Heidelberg, Heidelberg, Germany
| | - Irmgard Eichler
- Department of Pediatrics and Adolescent Medicine, University of Vienna, Vienna, Austria
| | - Hans H. Seydewitz
- Department of Pediatrics and Adolescent Medicine, Albert Ludwigs University, Freiburg, Germany
| | - Margarida D. Amaral
- Centre of Human Genetics, National Institute of Health Dr. Ricardo Jorge, Lisboa, Portugal
- Department of Chemistry and Biochemistry, Faculty of Sciences, University of Lisboa, Lisboa, Portugal
| | - Marcus A. Mall
- Division of Pediatric Pulmonology and Allergy and Cystic Fibrosis Center, Department of Pediatrics III, University of Heidelberg, Heidelberg, Germany
- Translational Lung Research Center, University of Heidelberg, Heidelberg, Germany
- * E-mail:
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Palmer ML, Peitzman ER, Maniak PJ, Sieck GC, Prakash YS, O'Grady SM. K(Ca)3.1 channels facilitate K+ secretion or Na+ absorption depending on apical or basolateral P2Y receptor stimulation. J Physiol 2011; 589:3483-94. [PMID: 21606112 DOI: 10.1113/jphysiol.2011.207548] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Human mammary epithelial (HME) cells express several P2Y receptor subtypes located in both apical and basolateral membranes. Apical UTP or ATP-γ-S stimulation of monolayers mounted in Ussing chambers evoked a rapid, but transient decrease in short circuit current (I(sc)), consistent with activation of an apical K+ conductance. In contrast, basolateral P2Y receptor stimulation activated basolateral K+ channels and increased transepithelial Na+ absorption. Chelating intracellular Ca2+ using the membrane-permeable compound BAPTA-AM, abolished the effects of purinoceptor activation on I(sc). Apical pretreatment with charybdotoxin also blocked the I(sc) decrease by >90% and similar magnitudes of inhibition were observed with clotrimazole and TRAM-34. In contrast, iberiotoxin and apamin did not block the effects of apical P2Y receptor stimulation. Silencing the expression of K(Ca)3.1 produced ∼70% inhibition of mRNA expression and a similar reduction in the effects of apical purinoceptor agonists on I(sc). In addition, silencing P2Y2 receptors reduced the level of P2Y2 mRNA by 75% and blocked the effects of ATP-γ-S by 65%. These results suggest that P2Y2 receptors mediate the effects of purinoceptor agonists on K+ secretion by regulating the activity of K(Ca)3.1 channels expressed in the apical membrane of HME cells. The results also indicate that release of ATP or UTP across the apical or basolateral membrane elicits qualitatively different effects on ion transport that may ultimately determine the [Na+]/[K+] composition of fluid within the mammary ductal network.
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Affiliation(s)
- Melissa L Palmer
- Biology Program, College of Biological Sciences, University of Minnesota, Minneapolis, MN 55455, USA
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Hug MJ, Derichs N, Bronsveld I, Clancy JP. Measurement of ion transport function in rectal biopsies. Methods Mol Biol 2011; 741:87-107. [PMID: 21594780 DOI: 10.1007/978-1-61779-117-8_7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Cystic fibrosis (CF) is caused by mutations in the gene encoding for the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR functions as an anion channel and is known to interact with a number of other cellular proteins involved in ion transport. To date more than 1,800 mutations are known, most of which result in various degrees of impaired transport function of the gene product. Due to the high inter-individual variability of disease onset and progression, CF still is a diagnostic challenge. Implemented almost 20 years ago, the measurement of electrolyte transport function of rectal biopsies is a useful ex vivo tool to diagnose CF. In this chapter we will review the different approaches to perform ion transport measurements and try to highlight the advantages and limitations of these techniques.
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Affiliation(s)
- Martin J Hug
- Pharmacy, University Medical Center Freiburg, D-79106, Freiburg, Germany.
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30
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Bachmann O, Juric M, Seidler U, Manns MP, Yu H. Basolateral ion transporters involved in colonic epithelial electrolyte absorption, anion secretion and cellular homeostasis. Acta Physiol (Oxf) 2011; 201:33-46. [PMID: 20528802 DOI: 10.1111/j.1748-1716.2010.02153.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Electrolyte transporters located in the basolateral membrane of the colonic epithelium are increasingly appreciated as elaborately regulated components of specific transport functions and cellular homeostasis: During electrolyte absorption, Na(+) /K(+) ATPase, Cl⁻ conductance, Cl⁻/HCO₃⁻ exchange, K(+) /Cl⁻ cotransport and K(+) channels are candidates for basolateral Na(+) , Cl⁻ and K(+) extrusion. The process of colonic anion secretion involves basolateral Na(+) /K(+) /2Cl⁻ , and probably also Na(+) /HCO₃⁻ cotransport, as well as Na(+) /K(+) ATPase and K(+) channels to supply substrate, stabilize the membrane potential and generate driving force respectively. Together with a multitude of additional transport systems, Na(+) /H(+) exchange and Na(+) /HCO₃⁻ cotransport have been implicated in colonocyte pH(i) and volume homeostasis. The purpose of this article is to summarize recently gathered information on the molecular identity, function and regulation of the involved basolateral transport systems in native tissue. Furthermore, we discuss how these findings can help to integrate these systems into the transport function and the cellular homoeostasis of colonic epithelial cells. Finally, disturbances of basolateral electrolyte transport during disease states such as mucosal inflammation will be reviewed.
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Affiliation(s)
- O Bachmann
- Department of Gastroenterology, Hepatology, and Endocrinology, Hannover Medical School, Germany.
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31
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Föller M, Bobbala D, Koka S, Boini KM, Mahmud H, Kasinathan RS, Shumilina E, Amann K, Beranek G, Sausbier U, Ruth P, Sausbier M, Lang F, Huber SM. Functional significance of the intermediate conductance Ca2+-activated K+ channel for the short-term survival of injured erythrocytes. Pflugers Arch 2010; 460:1029-44. [PMID: 20857305 DOI: 10.1007/s00424-010-0878-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 08/19/2010] [Accepted: 08/24/2010] [Indexed: 01/30/2023]
Abstract
Increased cytosolic Ca(2+) concentrations activate Gardos K(+) channels in human erythrocytes with membrane hyperpolarization, efflux of K(+), Cl⁻, and osmotically obliged H₂O resulting in cell shrinkage, a phenomenon referred to as Gardos effect. We tested whether the Gardos effect delays colloid osmotic hemolysis of injured erythrocytes from mice lacking the Ca(2+)-activated K(+) channel K(Ca)3.1. To this end, we applied patch clamp and flow cytometry and determined in vitro as well as in vivo hemolysis. As a result, erythrocytes from K(Ca)3.1-deficient (K(Ca)3.1(-/-)) mice lacked Gardos channel activity and the Gardos effect. Blood parameters, reticulocyte count, or osmotic erythrocyte resistance, however, did not differ between K(Ca)3.1(-/-) mice and their wild-type littermates, suggesting low or absent Gardos channel activity in unstressed erythrocytes. Oxidative stress-induced Ca(2+) entry and phospholipid scrambling were significantly less pronounced in K(Ca)3.1(-/-) than in wild-type erythrocytes. Moreover, in vitro treatment with α-toxin from Staphylococcus aureus, which forms pores in the cellular membrane, resulted in significantly stronger hemolysis of K(Ca)3.1(-/-) than of wild-type erythrocytes. Intravenous injection of α-toxin induced more profound hemolysis in K(Ca)3.1(-/-) than in wild-type mice. Similarly, intra-peritoneal application of the redox-active substance phenylhydrazine, an agent for the induction of hemolytic anemia, was followed by a significantly stronger decrease of hematocrit in K(Ca)3.1(-/-) than in wild-type mice. Finally, malaria infection triggered the activation of K(Ca)3.1 and transient shrinkage of the infected erythrocytes. In conclusion, K(Ca)3.1 channel activity and Gardos effect counteract hemolysis of injured erythrocytes, thus decreasing hemoglobin release into circulating blood.
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Affiliation(s)
- Michael Föller
- Department of Physiology, University of Tübingen, Tübingen, Germany
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Yu K, Lujan R, Marmorstein A, Gabriel S, Hartzell HC. Bestrophin-2 mediates bicarbonate transport by goblet cells in mouse colon. J Clin Invest 2010; 120:1722-35. [PMID: 20407206 DOI: 10.1172/jci41129] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 02/17/2010] [Indexed: 01/17/2023] Open
Abstract
Anion transport by the colonic mucosa maintains the hydration and pH of the colonic lumen, and its disruption causes a variety of diarrheal diseases. Cholinergic agonists raise cytosolic Ca2+ levels and stimulate anion secretion, but the mechanisms underlying this effect remain unclear. Cholinergic stimulation of anion secretion may occur via activation of Ca2+-activated Cl- channels (CaCCs) or an increase in the Cl- driving force through CFTR after activation of Ca2+-dependent K+ channels. Here we investigated the role of a candidate CaCC protein, bestrophin-2 (Best2), using Best2-/- mice. Cholinergic stimulation of anion current was greatly reduced in Best2-/- mice, consistent with our proposed role for Best2 as a CaCC. However, immunostaining revealed Best2 localized to the basolateral membrane of mucin-secreting colonic goblet cells, not the apical membrane of Cl--secreting enterocytes. In addition, in the absence of HCO3-, cholinergic-activated current was identical in control and Best2-/- tissue preparations, which suggests that most of the Best2 current was carried by HCO3-. These data delineate an alternative model of cholinergic regulation of colonic anion secretion in which goblet cells play a critical role in HCO3- homeostasis. We therefore propose that Best2 is a HCO3- channel that works in concert with a Cl:HCO3- exchanger in the apical membrane to affect transcellular HCO3- transport. Furthermore, previous models implicating CFTR in cholinergic Cl- secretion may be explained by substantial downregulation of Best2 in Cftr-/- mice.
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Affiliation(s)
- Kuai Yu
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Lam RS, Nahirney D, Duszyk M. Cholesterol-dependent regulation of adenosine A2A receptor-mediated anion secretion in colon epithelial cells. Exp Cell Res 2009; 315:3028-35. [DOI: 10.1016/j.yexcr.2009.06.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 06/08/2009] [Accepted: 06/08/2009] [Indexed: 11/29/2022]
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Düfer M, Gier B, Wolpers D, Krippeit-Drews P, Ruth P, Drews G. Enhanced glucose tolerance by SK4 channel inhibition in pancreatic beta-cells. Diabetes 2009; 58:1835-43. [PMID: 19401418 PMCID: PMC2712794 DOI: 10.2337/db08-1324] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Accepted: 04/22/2009] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Ca(2+)-regulated K(+) channels are involved in numerous Ca(2+)-dependent signaling pathways. In this study, we investigated whether the Ca(2+)-activated K(+) channel of intermediate conductance SK4 (KCa3.1, IK1) plays a physiological role in pancreatic beta-cell function. RESEARCH DESIGN AND METHODS Glucose tolerance and insulin sensitivity were determined in wild-type (WT) or SK4 knockout (SK4-KO) mice. Electrophysiological experiments were performed with the patch-clamp technique. The cytosolic Ca(2+) concentration ([Ca(2+)](c)) was determined by fura-2 fluorescence. Insulin release was assessed by radioimmunoassay, and SK4 protein was detected by Western blot analysis. RESULTS SK4-KO mice showed improved glucose tolerance, whereas insulin sensitivity was not altered. The animals were not hypoglycemic. Isolated SK4-KO beta-cells stimulated with 15 mmol/l glucose had an increased Ca(2+) action potential frequency, and single-action potentials were broadened. These alterations were coupled to increased [Ca(2+)](c). In addition, glucose responsiveness of membrane potential, [Ca(2+)](c), and insulin secretion were shifted to lower glucose concentrations. SK4 protein was expressed in WT islets. An increase in K(+) currents and concomitant membrane hyperpolarization could be evoked in WT beta-cells by the SK4 channel opener DCEBIO (100 micromol/l). Accordingly, the SK4 channel blocker TRAM-34 (1 micromol/l) partly inhibited K(Ca) currents and induced electrical activity at a threshold glucose concentration. In stimulated WT beta-cells, TRAM-34 further increased [Ca(2+)](c) and broadened action potentials similar to those seen in SK4-KO beta-cells. SK4 channels were found to substantially contribute to K(slow) (slowly activating K(+) current). CONCLUSIONS SK4 channels are involved in beta-cell stimulus-secretion coupling. Deficiency of SK4 current induces elevated beta-cell responsiveness and coincides with improved glucose tolerance in vivo. Therefore, pharmacologic modulation of these channels might provide an interesting approach for the development of novel insulinotropic drugs.
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Affiliation(s)
- Martina Düfer
- From the Institute of Pharmacy, the Department of Pharmacology, University of Tübingen, Tübingen, Germany
| | - Belinda Gier
- From the Institute of Pharmacy, the Department of Pharmacology, University of Tübingen, Tübingen, Germany
| | - Daniela Wolpers
- From the Institute of Pharmacy, the Department of Pharmacology, University of Tübingen, Tübingen, Germany
| | - Peter Krippeit-Drews
- From the Institute of Pharmacy, the Department of Pharmacology, University of Tübingen, Tübingen, Germany
| | - Peter Ruth
- From the Institute of Pharmacy, the Department of Pharmacology, University of Tübingen, Tübingen, Germany
| | - Gisela Drews
- From the Institute of Pharmacy, the Department of Pharmacology, University of Tübingen, Tübingen, Germany
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35
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Perry MD, Sandle GI. Regulation of colonic apical potassium (BK) channels by cAMP and somatostatin. Am J Physiol Gastrointest Liver Physiol 2009; 297:G159-67. [PMID: 19407217 PMCID: PMC2711756 DOI: 10.1152/ajpgi.00132.2009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
High-conductance apical K+ (BK) channels are present in surface colonocytes of mammalian (including human) colon. Their location makes them well fitted to contribute to the excessive intestinal K(+) losses often associated with infective diarrhea. Since many channel proteins are regulated by phosphorylation, we evaluated the roles of protein kinase A (PKA) and phosphatases in the modulation of apical BK channel activity in surface colonocytes from rat distal colon using patch-clamp techniques, having first increased channel abundance by chronic dietary K+ enrichment. We found that PKA activation using 50 micromol/l forskolin and 5 mmol/l 3-isobutyl-1-methylxanthine stimulated BK channels in cell-attached patches and the catalytic subunit of PKA (200 U/ml) had a similar effect in excised inside-out patches. The antidiarrheal peptide somatostatin (SOM; 2 micromol/l) had a G protein-dependent inhibitory effect on BK channels in cell-attached patches, which was unaffected by pretreatment with 10 micromol/l okadaic acid (an inhibitor of protein phosphatase type 1 and type 2A) but completely prevented by pretreatment with 100 micromol/l Na+ orthovanadate and 10 micromol/l BpV (inhibitors of phosphoprotein tyrosine phosphatase). SOM also inhibited apical BK channels in surface colonocytes in human distal colon. We conclude that cAMP-dependent PKA activates apical BK channels and may enhance colonic K+ losses in some cases of secretory diarrhea. SOM inhibits apical BK channels through a phosphoprotein tyrosine phosphatase-dependent mechanism, which could form the basis of new antidiarrheal strategies.
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Affiliation(s)
- M. D. Perry
- Institute of Molecular Medicine, St James's University Hospital, Leeds, United Kingdom
| | - G. I. Sandle
- Institute of Molecular Medicine, St James's University Hospital, Leeds, United Kingdom
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Bajwa PJ, Lee JW, Straus DS, Lytle C. Activation of PPARgamma by rosiglitazone attenuates intestinal Cl- secretion. Am J Physiol Gastrointest Liver Physiol 2009; 297:G82-9. [PMID: 19443733 DOI: 10.1152/ajpgi.90640.2008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The thiazolidinedione (TZD) drugs rosiglitazone (Ro) and pioglitazone (Po) are PPARgamma agonists in widespread clinical use as insulin-sensitizing agents in Type 2 diabetes. On the basis of recent evidence implicating PPARgamma as a positive modulator of intestinal epithelial differentiation, we hypothesized that TZD drugs might attenuate intestinal secretory function. To evaluate this possibility, we examined the effects of Ro and Po on electrogenic Cl- secretion [short-circuit current (I(sc))] in mouse intestinal segments and in cultured human intestinal epithelial cells (HT29-Cl.19A). As hypothesized, oral administration of Ro (20 mg.kg(-1).day(-1)) to mice for 8 days markedly reduced intestinal I(sc) responses to cAMP (forskolin)- and Ca2+ (carbachol)-dependent stimuli. In these Ro-treated mice, cholera toxin-induced intestinal fluid accumulation was reduced 65%. With continued Ro treatment, the I(sc) response to carbachol recovered significantly, whereas that to forskolin remained attenuated. Treatment of HT29 cells for 5 days with 10 muM Ro or Po in vitro brought about a similar hyposecretory state. In HT29 cells, the loss of cAMP-dependent Cl- secretion was attributable to a reduced expression of CFTR Cl- channel, KCNQ1 K+ channel, and Na-K-2Cl cotransporter-1 proteins. The transient loss of Ca2+-dependent Cl- secretion involved an impairment of basolateral Ca2+-stimulated K+ channel activity without a detectable loss of K(Ca)3.1 channel protein. Our results establish TZD drugs as important modulators of intestinal Cl- secretory function.
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Affiliation(s)
- Poonam J Bajwa
- Division of Biomedical Sciences, University of California, Riverside, CA 92521-0121, USA
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Hirota CL, McKay DM. Loss of Ca-mediated ion transport during colitis correlates with reduced ion transport responses to a Ca-activated K channel opener. Br J Pharmacol 2009; 156:1085-97. [PMID: 19298254 DOI: 10.1111/j.1476-5381.2009.00122.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND AND PURPOSE Epithelial surface hydration is critical for proper gut function. However, colonic tissues from individuals with inflammatory bowel disease or animals with colitis are hyporesponsive to Cl(-) secretagogues. The Cl(-) secretory responses to the muscarinic receptor agonist bethanechol are virtually absent in colons of mice with dextran sodium sulphate (DSS)-induced colitis. Our aim was to define the mechanism underlying this cholinergic hyporesponsiveness. EXPERIMENTAL APPROACH Colitis was induced by 4% DSS water, given orally. Epithelial ion transport was measured in Ussing chambers. Colonic crypts were isolated and processed for mRNA expression via RT-PCR and protein expression via immunoblotting and immunolocalization. KEY RESULTS Expression of muscarinic M(3) receptors in colonic epithelium was not decreased during colitis. Short-circuit current (I(SC)) responses to other Ca(2+)-dependent secretagogues (histamine, thapsigargin, cyclopiazonic acid and calcium ionophore) were either absent or severely attenuated in colonic tissue from DSS-treated mice. mRNA levels of several ion transport molecules (a Ca(2+)-regulated Cl(-) channel, the intermediate-conductance Ca(2+)-activated K(+) channel, the cystic fibrosis transmembrane conductance regulator, the Na(+)/K(+)-ATPase pump or the Na(+)/K(+)/2Cl(-) co-transporter) were not reduced in colonic crypts from DSS-treated mice. However, protein expression of Na(+)/K(+)-ATPase alpha1 subunits was decreased twofold during colitis. Activation of Ca(2+)-activated K(+) channels increased I(SC) significantly less in DSS colons compared with control, as did the protein kinase C activator, phorbol 12-myristate 13-acetate. CONCLUSIONS AND IMPLICATIONS Decreased Na(+)/K(+)-ATPase expression probably contributes to overall epithelial hyporesponsiveness during colitis, while dysfunctional K(+) channels may account, at least partially, for lack of epithelial secretory responses to Ca(2+)-mediated secretagogues.
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Affiliation(s)
- Christina L Hirota
- Intestinal Disease Research Programme, Department of Pathology and Molecular Medicine, McMaster University, 3330 Hospital Drive Northwest, Calgary, Alberta, Canada.
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38
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Heitzmann D, Warth R. Physiology and pathophysiology of potassium channels in gastrointestinal epithelia. Physiol Rev 2008; 88:1119-82. [PMID: 18626068 DOI: 10.1152/physrev.00020.2007] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial cells of the gastrointestinal tract are an important barrier between the "milieu interne" and the luminal content of the gut. They perform transport of nutrients, salts, and water, which is essential for the maintenance of body homeostasis. In these epithelia, a variety of K(+) channels are expressed, allowing adaptation to different needs. This review provides an overview of the current literature that has led to a better understanding of the multifaceted function of gastrointestinal K(+) channels, thereby shedding light on pathophysiological implications of impaired channel function. For instance, in gastric mucosa, K(+) channel function is a prerequisite for acid secretion of parietal cells. In epithelial cells of small intestine, K(+) channels provide the driving force for electrogenic transport processes across the plasma membrane, and they are involved in cell volume regulation. Fine tuning of salt and water transport and of K(+) homeostasis occurs in colonic epithelia cells, where K(+) channels are involved in secretory and reabsorptive processes. Furthermore, there is growing evidence for changes in epithelial K(+) channel expression during cell proliferation, differentiation, apoptosis, and, under pathological conditions, carcinogenesis. In the future, integrative approaches using functional and postgenomic/proteomic techniques will help us to gain comprehensive insights into the role of K(+) channels of the gastrointestinal tract.
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Affiliation(s)
- Dirk Heitzmann
- Institute of Physiology and Clinic and Policlinic for Internal Medicine II, Regensburg, Germany
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Sørensen MV, Matos JE, Sausbier M, Sausbier U, Ruth P, Praetorius HA, Leipziger J. Aldosterone increases KCa1.1 (BK) channel-mediated colonic K+ secretion. J Physiol 2008; 586:4251-64. [PMID: 18617563 DOI: 10.1113/jphysiol.2008.156968] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Mammalian K(+) homeostasis results from highly regulated renal and intestinal absorption and secretion, which balances the unregulated K(+) intake. Aldosterone is known to enhance both renal and colonic K(+) secretion. In mouse distal colon K(+) secretion occurs exclusively via luminal K(Ca)1.1 (BK) channels. Here we investigate if aldosterone stimulates colonic K(+) secretion via BK channels. Luminal Ba(2+) and iberiotoxin (IBTX)-sensitive electrogenic K(+) secretion was measured in Ussing chambers. In vivo aldosterone was augmented via a high K(+) diet. High K(+) diet led to a 2-fold increase of luminal Ba(2+) and IBTX-sensitive short-circuit current in distal mouse colonic mucosa. This effect was absent in BK alpha-subunit-deficient (BK(-/-)) mice. The resting and diet-induced K(+) secretion was stimulated by luminal ionomycin. In BK(-/-) mice luminal ionomycin did not stimulate K(+) secretion. In vitro addition of aldosterone likewise triggered a 2-fold increase in K(+) secretion, which was inhibited by the mineralocorticoid receptor antagonist spironolactone and the BK channel blocker IBTX. Semi-quantification of mRNA from colonic crypts showed up-regulation of BK alpha- and beta(2)-subunits in high K(+) diet mice. The BK channel could be detected luminally in colonic crypt cells by immunohistochemistry. The expression level of the channel in the luminal membrane was strongly up-regulated in K(+)-loaded animals. Taken together, these data strongly suggest that aldosterone-induced K(+) secretion occurs via increased expression of luminal BK channels.
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Affiliation(s)
- Mads V Sørensen
- Institute of Physiology and Biophysics, The Water and Salt Research Center, University of Aarhus, 8000 Aarhus C, Denmark
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Bajwa PJ, Alioua A, Lee JW, Straus DS, Toro L, Lytle C. Fenofibrate inhibits intestinal Cl- secretion by blocking basolateral KCNQ1 K+ channels. Am J Physiol Gastrointest Liver Physiol 2007; 293:G1288-99. [PMID: 17916649 DOI: 10.1152/ajpgi.00234.2007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Fibrates are peroxisome proliferator-activated receptor-alpha (PPARalpha) ligands in widespread clinical use to lower plasma triglyceride levels. We investigated the effect of fenofibrate and clofibrate on ion transport in mouse intestine and in human T84 colonic adenocarcinoma cells through the use of short-circuit current (I(sc)) and ion flux analysis. In mice, oral administration of fenofibrate produced a persistent inhibition of cAMP-stimulated electrogenic Cl(-) secretion by isolated jejunum and colon without affecting electroneutral fluxes of (22)Na(+) or (86)Rb(+) (K(+)) across unstimulated colonic mucosa. When applied acutely to isolated mouse intestinal mucosa, 100 microM fenofibrate inhibited cAMP-stimulated I(sc) within 5 min. In T84 cells, fenofibrate rapidly inhibited approximately 80% the Cl(-) secretory responses to forskolin (cAMP) and to heat stable enterotoxin STa (cGMP) without affecting the response to carbachol (Ca(2+)). Both fenofibrate and clofibrate inhibited cAMP-stimulated I(sc) with an IC(50) approximately 1 muM, whereas other PPARalpha activators (gemfibrozil and Wy-14,643) were without effect. Membrane permeabilization experiments on T84 cells indicated that fenofibrate inhibits basolateral cAMP-stimulated K(+) channels (putatively KCNQ1/KCNE3) without affecting Ca(2+)-stimulated K(+) channel activity, whereas clofibrate inhibits both K(+) pathways. Fenofibrate had no effect on apical cAMP-stimulated Cl(-) channel activity. Patch-clamp analysis of HEK-293T cells confirmed that 100 microM fenofibrate rapidly inhibits K(+) currents associated with ectopic expression of human KCNQ1 with or without the KCNE3 beta-subunit. We conclude that fenofibrate inhibits intestinal cAMP-stimulated Cl(-) secretion through a nongenomic mechanism that involves a selective inhibition of basolateral KCNQ1/KCNE3 channel complexes. Our findings raise the prospect of fenofibrate as a safe and effective antidiarrheal agent.
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Affiliation(s)
- Poonam J Bajwa
- Division of Biomedical Sciences, University of California, Riverside, CA 92521-0121, USA
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Flores CA, Melvin JE, Figueroa CD, Sepúlveda FV. Abolition of Ca2+-mediated intestinal anion secretion and increased stool dehydration in mice lacking the intermediate conductance Ca2+-dependent K+ channel Kcnn4. J Physiol 2007; 583:705-17. [PMID: 17584847 PMCID: PMC2277011 DOI: 10.1113/jphysiol.2007.134387] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Intestinal fluid secretion is driven by apical membrane, cystic fibrosis transmembrane conductance regulator (CFTR)-mediated efflux of Cl- that is concentrated in cells by basolateral Na(+)-K(+)-2Cl- cotransporters (NKCC1). An absolute requirement for Cl- efflux is the parallel activation of K(+) channels which maintain a membrane potential that sustains apical anion secretion. Both cAMP and Ca(2+) are intracellular signals for intestinal Cl- secretion. The K(+) channel involved in cAMP-dependent secretion has been identified as the KCNQ1-KCNE3 complex, but the identity of the K(+) channel driving Ca(2+)-activated Cl- secretion is controversial. We have now used a Kcnn4 null mouse to show that the intermediate conductance IK1 K(+) channel is necessary and sufficient to support Ca(2+)-dependent Cl- secretion in large and small intestine. Ussing chambers were used to monitor transepithelial potential, resistance and equivalent short-circuit current in colon and jejunum from control and Kcnn4 null mice. Na(+), K(+) and water content of stools was also measured. Distal colon and small intestinal epithelia from Kcnn4 null mice had normal cAMP-dependent Cl- secretory responses. In contrast, they completely lacked Cl- secretion in response to Ca(2+)-mobilizing agonists. Ca(2+)-activated electrogenic K(+) secretion was increased in colon epithelium of mice deficient in the IK1 channel. Na(+) and water content of stools was diminished in IK1-null animals. The use of Kcnn4 null mice has allowed us to demonstrate that IK1 K(+) channels are solely responsible for driving intestinal Ca(2+)-activated Cl- secretion. The absence of this channel leads to a marked reduction in water content in the stools, probably as a consequence of decreased electrolyte and water secretion.
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Affiliation(s)
- Carlos A Flores
- Centro de Estudios Científicos, Avenida Arturo Prat 514, Valdivia, Chile
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